
Each spring and fall, billions of birds migrate. In autumn, they head south from North America. Most birds travel at night because the winds are calmer and there are fewer predators. Raptors migrate during the day, giving songbirds and others a chance to stay safe at night. Have you ever thought about why birds migrate?
Birds migrate for several reasons, but some benefit ecosystems more than the birds themselves. One reason for migration is food. In North America, during spring and summer, there can be plenty of food from insects and the seeds and fruits of plants. When fall comes, it gets colder, most insects disappear, and plants stop growing, so the birds head south to find more food.
In the spring, birds migrate northward to breed. Northern forests and areas of open land in North America are less crowded than tropical forests. So, birds can more easily find suitable nesting sites to raise their young. A factor that we often overlook is the amount of daylight. During the breeding season, birds need plenty of daylight to care for their young, feed them, and teach them to fly. At the equator, daylight lasts around 12 hours year-round. But farther north, especially in Arctic areas, summer daylight lasts much longer. This benefits nesting birds. Longer days and more sunshine also mean that plants grow and produce seeds, and insects are abundant for the birds to eat.
Avoiding cold temperatures is another factor in why birds migrate, but it is not as important as you might think. In fact, some birds migrate not to areas closer to the equator, but farther south, where there’s more daylight. When the Northern Hemisphere is in winter, the Southern Hemisphere is enjoying summer. So, some birds—such as Arctic terns and bar-tailed godwits—travel from one extreme of the Northern Hemisphere far down into the Southern Hemisphere.
There is another factor in why birds migrate. In some cases, migration benefits the ecosystem more than the birds. As birds migrate, they benefit other plants and animals along the way. That doesn’t fit the “survival of the fittest” concept of evolution. Migrating birds can also help other animals by serving as prey and help plants by scattering seeds.
The bottom line is that birds migrate for several reasons. Migrations benefit birds directly, but they also benefit other plants and animals along their migration route and in the areas where they stop. Looking at the whole picture, we see a designed system. It is a system that provides for the birds and nourishes the ecosystems of planet Earth. There is more to bird migration that indicates system design, and we’ll look at other factors tomorrow.
— Roland Earnst © 2026









